1. Field of the Invention
This invention relates generally to separation mechanisms and, in particular, it relates to separation mechanisms adapted for retaining and remotely releasing bolts or other retained elements from engagement with various structures, such as spacecraft, to deploy objects, instrumentation, and equipment from the structures.
2. Description of the Prior Art
Spacecraft are useful for deploying payloads of equipment from a storage bay upon reaching a certain extraterrestrial location or orbit. The equipment that is deployed may include antennae, instrumentation, solar arrays, and communication systems that are often highly sensitive in nature and that must, therefore, be adequately restrained and protected during launch of the spacecraft and that must be deployed with minimal vibration, shock, or contamination to avoid damaging the equipment. Due to factors such as launch and repair costs and weight and power constraints, the space industry further demands that the device utilized for retaining and remotely releasing the equipment (i.e., the separation mechanism) comply with other design criteria including single fault tolerance, redundancy for critical features, minimal weight, wear and corrosion resistance, and efficient power consumption. It is also generally desirable that the separation mechanism that is installed in the spacecraft be testable to provide assurance that the mechanism will function as intended and be resettable after such testing or after use, i.e., be reusable.
A number of separation mechanisms have been employed to provide these retention and remote release functions while attempting to meet the space industry""s other stringent design criteria. For example, pyrotechnic separation mechanisms, such as pin pullers, separation nuts, and cable cutters, have been used in spacecraft to release payloads. However, the use of pyrotechnic separation mechanisms is generally undesirable in spacecraft because of the large vibration and shock forces developed when the mechanism is fired or exploded, the potential of chemical contamination if a seal fails, the susceptibility of pyrotechnic devices to inadvertent ignition caused by electrostatic build-up or stray electric signals, and the inability to test, reset, or reuse such devices. Other separation mechanisms have employed burn-wire devices that generally operate by restraining a tensile force, e.g., a spring, with a filament or initiator that is ignited or melted to release or separate a retained element. As with the pyrotechnic separation devices, burn-wire devices can only be used once and cannot be effectively tested and then reset. More recently, separation mechanisms have employed shape memory alloys, generally as actuators, in an attempt to meet the needs of the space industry. See, for example, U.S. Pat. No. 5,771,742 to Bokaie et al. and U.S. Pat. No. 5,312,152 to Woebkenberg, Jr. et al. However, these mechanisms often require significant amounts of power and/or inefficiently use power and are relatively heavy.
Despite the ongoing efforts to meet the requirements of the space industry, there remains a demand for an improved separation mechanism that effectively satisfies the deployment needs of the space and other industries while overcoming the foregoing and other shortcomings of the prior art separation mechanisms.
Accordingly, it is a general object of the present invention to provide an improved separation mechanism for securely retaining and controllably releasing a fastener or other object.
It is a more specific object of the present invention to provide an improved separation mechanism that releases a fastener or other object with reduced vibration and shock forces and with minimal or no risk of chemical or other contamination of nearby equipment.
It is related specific object of the present invention to provide a separation mechanism that efficiently uses power, is compact and lightweight, is testable, and is resettable, i.e., is useful for repetitive operations.
It is another general object of the present invention to provide an improved separation mechanism that provides redundancy of critical features, is single-fault tolerant, and meets other specific design criteria, such as corrosion and wear resistance, established by the space industry.
It is a related specific object of the present invention to provide such a separation mechanism that can readily be used or retrofitted into existing and planned space industry release systems to utilize typical pyrotechnic firing circuits and/or heater circuits to trigger the separation mechanism.
Additional objects, advantages, and novel features of the invention are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures or may be learned by practicing the invention. Further, the objects and the advantages may be realized and attained by means of the instrumentalities and in combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects and in accordance with the purposes of the present invention, as embodied and broadly described herein, the separation mechanism includes a self-aligning release assembly that can be selectively positioned into locked and released positions at which a fastener or other object is securely retained within and released from the separation mechanism, respectively. The release assembly is positioned within a protective housing that can be mounted via an included mounting base to a structure, e.g., a spacecraft storage bay, to facilitate deployment of instrumentation, power and communication equipment, and the like from the structure. The release assembly includes a flywheel with an internal bearing race, a plurality of bearing elements contacting the bearing race, a positioning element within and adjacent the flywheel for aligning and retaining the bearing elements, and a segmented nut centrally positioned within the flywheel with the outer surfaces of the nut segments abutting the bearing elements. In the locked position of the separation mechanism, the bearing elements forcibly urge the nut segments radially inward to retain a fastener or other objects and with an inward force sufficient to resist any outward forces applied by the retained object. When the flywheel is rotated to the released position, the positioning element aligns the bearing elements with recessed portions on the bearing race of the flywheel. The bearing elements roll into the recessed portions, and the segmented nut is separated, i.e., pushed radially outward by forces developed between the nut and the retained object during initial tightening, so as to release the retained object. The separation mechanism further includes an actuating assembly that utilizes shape memory alloy wires to trigger the mechanism by pulling or moving a latch from a toggle-locked position to an unlocked position at which one or more drive springs rotate the flywheel to the released position. The separation mechanism can then be reset, without rewiring or retesting, with accurate alignment of the bearings, the segmented nut, and other components to facilitate reuse of the separation mechanism.